484 ALFRED GIBBS BOUR^'E. 



16. 7. — Hirudo. Diagram of a nephridium. a. Funnel, h—c. Testis 

 lobe, c — d. Main lobe, e — d. Tliat portion of the main lobe not repre- 

 sented in Clepsine. e. Point where the recurrent ductules leave the 

 main lobe on their way to the apex g, and where the recurrent duct re- 

 enters the main lobe when returning from the apex g. e—f. Recurrent 

 lobe ; for the remainder of their course the recurrent ductules and duct 

 traverse the apical lobe, /— ^. g- Apex and point where the recurrent 

 ductules collect to form the recurrent duct; this latter, as in Clepsine, 

 returns to e, re-enters there the main lobe, emerges thence at h to pass 

 across to the apex, and traversing the apical lobe returns to /, where it 

 passes across into the free end of the main lobe d ; it emerges from the 

 main lobe at h. h—j. the vesicle duct (efferent duct), j — k. The vesicle. 

 /. The aperture to the exterior. 



A B, CD, E r, G H. Sections through the regions so marked. «, n. 

 Nuclei. 



Section a b shows the cells of the main lobe, with their branching 

 ductules ; the nuclei of these cells are drawn but not lettered. The cells 

 are grouped around two perforated cells, ■which contain the "recurrent" 

 and " main " portions of the duct, n, n. Nuclei in the walls of these 

 perforated cells. 



Section c d passes through the ccecal end of the main lobe, and also 

 through the recurrent lobe. The main lobe section shows similar arrange- 

 ments to those shown in the Section a b. The section through the recur- 

 rent lobe shows the recurrent ductules branching in the cells, which are 

 grouped around the perforated cell containing the recurrent duct. 



Section e f passes through one of the perforated cells containing the 

 vesicle duct. 



Section g ii passes through the numerous cells bounding the duct in 

 the last portion of its course, and lined internally by a prolongation of 

 the cuticle from the body surface. 



